Hydrolastic height problem??

[rolesyboy]

Filled the suspension with fluid and whilst the front and back both go up, the backs seem to go up a hell of a lot more than the front end. Car hasn't been used for years and the front has cleared the ST type bump stops but it really looks ridiculous at the back like a jacked up 70's street machine. Any reason for this? Cheers

[scooperman]

do you have the rear helper springs installed? If they are missing or disconnected the rear trailing arms will be pushed down excessively.

[carbon]

If the rear end is sitting too high just let some fluid out, and the rear will come down more then the front.

[rolesyboy]

Yes both helper springs in situ. The front sits mm's above the bump stops and the rear sits like a drag car ie a good 6-7 inches from the standard tyres???? Could it be anything else?

[gr4h4m]

The book specs a pressure and ride height. What did you set yours too? I went off of the ride height. Did you use the vac side of the pump first before putting fluid in?

When I last did mine it does go up at the back more but settled out after a bit of moving about. Ie bouncing up and down. Does seem a bit strange tho. Is the front even?

[Gray]

If the displacers were not the originals then you may have mismatched pistons front / rear, they are 2 sizes that I'm aware of one is 3mm taller than the other,if the taller is on the rear it can give something like a 5 to 1 ratio increase, also there are 2 different length rear displacer struts available.

[rolesyboy]

Cheers guys. It is a favour for a mate. Will take on bpard your suggestions although it may just need the front unions cracking off and some air bleeding out. Not used a vacuum pump. Just a liquid levers thing. Thanks. Mark

[66S]

You should probably vacuum the system to get everything correct before you start looking for problems. The rear springs may be weakened by age and there are two versions of the springs. The later one is beefier and longer in the coil section. From there the rear displacer pistons can be shortened, as can the displacer struts.

Al

[Smiffy]

As Al's say above is you need to purge the system of air, to do this you fill it up and then use the vacuum side of the proper pump to suck all the fluid out which hopefully will bring all the air with it. Mind you it can take a few attempts to get it all out.

[rolesyboy]

Thanks fo rthe comments guys. I have a liquid levers pump without a vacuum and so that won't be happening. Will crack a union off at the front if it doesn't settle down. Cheers. Mark

[66S]

The trouble is, dropping the fluid will not expel all the air, that is why we are suggesting it be sucked under vacuum. The lever pump you are using is only any good for maintenance, major services should be done with a factory type Churchhill pump.

Regards
Al

[nick@dunsdale]

if the front is really low it could also be f@*ked knuckle joints

fair bit easier to get out of a wet mini for quick inspection

all else fails the old washer trick will level it up lol

[IAIN]

With the liquid levers pump connected and open, try jacking the car up then push the wheels up to flush all the fluid out of the units. Then try again.

Have you thought about the problem being at the front ie, it's too low at the front rather than the back too high ?
If the suspension knuckles and nylon cups were worn out that would make it sit low, while you pump more preasure in to raise the front making the sit up ?


EDIT Nick, great minds think alike !

[rolesyboy]

This was the lines I was thinking along. Will have a look and report back. Cheers. Mark

[formulaphoto]

You can also "bleed" the system without a vacuum pump. It's a little messy, but just loosen the front hoses a few turns and pump it while it "leaks out"..as if bleeding brakes, etc.

W

[rolesyboy]

Thanks Warwick. That is what I meant by cracking the unions off at the front. I think this was lost in translation. Many thanks. Mark

[scooperman]

Go to the Mk1PerformanceConversions site and...oh wait, we are here. So take a look at the "Make Your Own Wet Suspender Pump" article on the technical page http://mk1-performance-conversions.co.u ... anical.htm. I used the information in that article to make my own vacuum/fill tank when I replaced the hoses on my displacers. Here is a picture of my tank.
.

Since this was for a Riley Elf, I posted my how-to pictures in a hydro repair thread on the Elf/Hornet Register forum last year, its at http://elf-hornet.4forum.biz/t1303-hydr ... o-dry-cone . My focus was mostly on whether I could fix/replace hoses and then pressure test the displacers out of the car, but maybe there is something there that might help you.

[66S]

You can also "bleed" the system without a vacuum pump. It's a little messy, but just loosen the front hoses a few turns and pump it while it "leaks out"..as if bleeding brakes, etc.W

When I had a displacer in my test jig, I applied vacuum to it to see what it did and it actually draws the diaphragm in, reducing the size of the fluid cavity. There is no way you could do that by simply letting the pressure go. For what it's worth !

Al

[formulaphoto]

You can also "bleed" the system without a vacuum pump. It's a little messy, but just loosen the front hoses a few turns and pump it while it "leaks out"..as if bleeding brakes, etc.W

When I had a displacer in my test jig, I applied vacuum to it to see what it did and it actually draws the diaphragm in, reducing the size of the fluid cavity. There is no way you could do that by simply letting the pressure go. For what it's worth !

Al

Interesting...good to know! I actually have the use of a Churchill pump. but the vacuum side doesn't work (lever seems seized) and the pressure gauge is in-op too.